ADVANCES
20 Scientific American, April 2022
Barry Webb (all images)When Barry Webb is crawling around on the forest floor
with a flashlight, passersby understandably give him
strange looks. The U.K.-based photographer is hunting
for something others might struggle to see: slime mold
growths that stand less than a tenth of an inch high.
For scientists, classifying slime molds has proved as slip-
pery as the name suggests. These life-forms have previously
been labeled plants, fungi and even animals, but they are
actually lesser-known organisms called protists. Slime
molds coat wet and decaying surfaces, including dead trees,
leaf litter and dung, often functioning as a single cell with
many nuclei. Just before dying, they send up fruiting bodies
to reproduce, which Webb catches on camera.
Each of Webb’s images consists of 30 to 100 photo-
graphs taken with different focal points. When assembled,
the composite shows more detail than any one snapshot
could. Most specimens Webb captures are in the woods
near his home in England’s Buckinghamshire County, but
some grow on decaying logs he keeps in his garden to see
what might emerge. If you would like to try something
similar, it is easy to do—just beware of hungry slugs,
Webb warns.
- Comatricha nigra grows on a fallen beech log just before
releasing its spores. Many slime molds, including those in
this genus, find the perfect place to settle down by scoot-
ing around via pseudopods—cellular extensions that shoot
forward for the rest of the cell to coalesce around. - Metatrichiafloriformis’s sprouted casings crack open
as they dry out, allowing wind to lift away spores that
eventually form into amoebalike creatures. These organ-
isms can harden into a stationary cyst or grow a “tail”
and move around, depending on how wet their final
destination is. - Cribraria aurantiaca produces vivid fruiting bodies. Slime
molds such as C. aurantiaca always occupy new patches of
wet logs or other surfaces; they leave residue behind as they
move and avoid places already streaked with their goo. - Physarumleucophaeumline the edge of a beech leaf.
These slime molds are impressive problem solvers.
Researchers have plopped other members of the genus
Physarum into mazes and watched them find the shortest
path through. Physarum has even inspired a slime mold
algorithm that researchers deployed to map filaments of
dark matter connecting galaxies throughout the universe.
To see more, visit ScientificAmerican.com/science-in-images
B I O L O G YScience
in Images
By Leslie Nemo
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